title: Characterization of chromosomal damage accumulated in freeze-dried mouse spermatozoa preserved under ambient and heat stress conditions.
abstract: Structural chromosome aberrations and DNA damage generated in freeze-dried mouse spermatozoa were investigated. Freeze-dried sperm samples were preserved at 4, 25 and 50°C for short duration (1 day to 2 months) and at 25°C for long duration (2 years). The spermatozoa were injected into mouse oocytes to analyse the chromosomes of the zygotes at the first cleavage metaphase. Chromosome break of the chromosome-type aberrations was the most common type of structural chromosome aberrations observed in all freeze-dried samples. The frequency of chromatid exchanges rapidly increased in freeze-dried spermatozoa preserved at 50°C for 1-5 days. The frequency of chromatid-type aberrations (break and exchange) gradually increased in freeze-dried spermatozoa preserved at 25°C for up to 2 months. Alkaline comet assay revealed significant migration of damaged DNA accumulated in freeze-dried spermatozoa preserved at 50°C for 3 days and 25°C for 2 years. However, no DNA damage was detected using the same sperm samples by neutral comet assay, which can detect mostly DNA double-strand breaks in cellular DNA. These results suggest that DNA single-strand breaks were accumulated in freeze-dried spermatozoa preserved under ambient or heat conditions, and then chromatid-type aberrations, especially the chromatid exchanges, were formed via post-replication repair system in zygotes.
authors.affiliation: Department of Biological Sciences, Asahikawa Medical University, 2-1-1-1 Midorigaoka Higashi, Asahikawa 078-8510, Japan. hkusa55@asahikawa-med.ac.jp
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Kusakabe
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tateno
mesh_terms: D000818:Animals; D002869:Chromosome Aberrations; D020552:Comet Assay; D004249:DNA Damage / Q000235:genetics*; D004260:DNA Repair / Q000235:genetics; D005260:Female; D005612:Freeze Drying; D008297:Male; D051379:Mice; D009865:Oocytes / Q000502:physiology; D020554:Sperm Injections, Intracytoplasmic; D013094:Spermatozoa / Q000473:pathology*; D018709:Statistics, Nonparametric; D013696:Temperature; D013997:Time Factors